New research suggests that regular consumption of fizzy drinks containing artificial sweeteners, particularly aspartame, may elevate the risk of heart and brain damage. Aspartame, commonly found in products like Diet Coke, Pepsi Max, Sprite, and Extra chewing gum, has been a subject of ongoing health concerns, previously linked to conditions such as certain cancers, high blood pressure, and stroke.

Spanish researchers have now added to these concerns, indicating that high levels of aspartame intake could lead to accelerated brain aging and stiffening of the heart. A study conducted on mice revealed that higher aspartame consumption, roughly equivalent to three servings every fortnight in humans, was associated with an approximate 20 percent increased risk of mild cardiac hypertrophy, a condition characterized by a thickened heart muscle, alongside accelerated cognitive decline. Interestingly, the study also observed a nearly 20 percent reduction in body fat among the animals.

The researchers, from the Centre for Cooperative Research in Biomaterials in San Sebastián, published their findings in the journal Biomedicine and Pharmacotherapy. They urged regulatory officials to re-evaluate current aspartame consumption guidelines. Their findings suggest that while aspartame did reduce fat deposits by 20 percent in mice, it came at the cost of mild cardiac hypertrophy and decreased cognitive performance. They concluded that 'aspartame at permitted doses can compromise the function of major organs, and so it would be advisable to reassess the safety limits for humans.'

In the study, mice received a dose of 7mg of aspartame per kilogram of body weight, administered over three consecutive days every two weeks. This dosage contrasts with the advice from the World Health Organization (WHO), the European Medicines Agency (EMA), and the US Food and Drug Administration (FDA), which recommend that people consume no more than 50mg per kilogram of body weight per day.

Over a year-long follow-up period, the aspartame-exposed mice exhibited a significant reduction in heart output—falling by 26 percent in the left ventricle and 20 percent in the right. The study also noted a 25 percent reduction in septal curvature, the muscular wall separating the heart's ventricles. Furthermore, the mice displayed 'signs of altered neurobehavior' and 'possible pathophysiological changes in the brain'. However, the scientists acknowledged limitations, including the study's duration, emphasizing the need for longer-term research.

The International Sweeteners Association (ISA) has called for caution in interpreting these findings, arguing that they cannot be directly applied to humans. Laurent Oger, Director General at the ISA, highlighted key physiological differences between humans and mice, such as metabolism, lifespan, cardiac physiology, and brain energy utilisation, which limit the direct relevance of the study's conclusions. Oger also pointed out that the observed reduction in body weight and fat mass in mice contradicts evidence from human clinical trials, which suggest that aspartame and other low or no-calorie sweeteners do not inherently affect body weight but may support weight management by reducing sugar intake. He added that the reported cardiac and neurobehavioral alterations occurred in aged mice, making it challenging to differentiate potential aspartame-related effects from normal aging processes. The ISA maintains that aspartame has been extensively researched and approved as safe by global food safety authorities.

Previously, concerns about a link between artificial sweeteners and cancer led the World Health Organization to classify aspartame as 'possibly carcinogenic to humans' in 2023. However, the UN agency clarified that this risk pertained only to very high levels of consumption, estimating that an 11-stone (70kg) adult could safely consume approximately 14 cans of diet fizzy drinks daily.